Study links antidepressants use during pregnancy to autism risk

Physicians note risks is small and say further study is needed

Quebec researchers say they have found an association between women who take antidepressants in mid- to late pregnancy and a higher risk of autism in their babies.

But while their study found the risk of autism almost doubled for children whose mothers took the drugs during second and third trimesters, it still amounted to a small number of babies affected — about 1.2 per cent, which falls within the range of autism prevalence rates.

Use of antidepressants, particularly those known as selective serotonin reuptake inhibitors (SSRIs), and using more than one type of medication in the last six months of pregnancy “increases the risk of autism spectrum disorder in children, even after considering maternal depression,” the study concludes.

However, physicians in the field and an accompanying editorial in the journal, noted the risk is still small and urged caution when it comes to interpreting the results because it’s difficult to separate the impact of antidepressants on a developing fetus from the impact of the underlying mental health issues or other genetics.

“The study is not there to worry anyone,” study co-author Anick Berard, professor of pharmacy at the University of Montreal, said in an interview.

“It’s to give (mothers-to-be) extra data to make better informed decisions when having depression and contemplating treatment options, and also give data to the prescribing physicians.”

The study looked at 145,456 full-term babies born in Quebec between 1998 and 2009. It found that of the 2,532 infants born to women taking antidepressants during the last six months of pregnancy, 31 babies — or 1.2 per cent — were later diagnosed with autism.

That compares with 0.7 per cent of babies (1,008 of 140,732) who were diagnosed but whose mothers did not use antidepressants.

Use of the drugs during the first trimester was not associated with higher risks of autism.

The prevalence of autism, a neurodevelopmental disorder that affects communication, behaviour and learning, has skyrocketed over the past 15 years and is estimated to affect anywhere from 1 per cent to as many as 1 of every 68 children.

The Quebec researchers cited statistics showing 4.5 per cent of pregnant women in Canada reported using antidepressants between 2001 and 2006, but a news release from University of Montreal said 6 to 10 per cent use the medication.

The Quebec study is observational and does not show causation, Berard said. But she called it one more “piece of the puzzle” as researchers strive to uncover some of the complex and interacting environmental and genetic factors that play a role in autism.

Depression should be treated, Berard added. But she said the majority of pregnant women with a diagnosis have mild to moderate cases that may be effectively treated through options such as psychological therapy and exercise.

A JAMA Pediatrics editorial also released Monday cautioned that the findings must be weighed against other risks, including the impact of untreated maternal depression, which can hinder infant development and has been linked to other complications such as preterm birth and low birth weights.

And it noted the study does little to clarify the issue for women struggling with whether or not to take medication while pregnant.

“It makes no more sense to suggest that (antidepressants) should always be avoided than to say that they should never be stopped,” wrote psychiatrist Dr. Bryan King of Seattle Children’s Hospital, adding that autism and potential causes of the neurodevelopmental disorder are complex.

While studying antidepressant use in pregnancy is important, it’s also very difficult to separate the effects of the medication versus the impact of the underlying depression that causes women to take the drugs, said Dr. Simone Vigod of Women’s College Hospital.

Even if the study findings are accurate, “we’re talking about really, really small numbers,” said Vigod, psychiatrist and researcher and head of the hospital’s reproductive life stages program.

“I think we have to be fairly cautious about interpreting it and make sure we’re not making women who really, really require these medications frightened.”